1. Field
A rechargeable lithium battery is disclosed.
2. Description of the Related Art
Wide use of battery-operated electronic devices, such as mobile phones, camcorders, laptop computers and electric cars, has created a demand for high energy density batteries as power sources for these devices.
A rechargeable lithium battery typically includes a negative electrode including a carbonaceous material capable of absorbing and releasing (intercalating/deintercalating) lithium ions, a positive electrode including a lithium-containing oxide, and/or the like, and an electrolyte including a lithium salt dissolved in an organic solvent. During the initial charge of a rechargeable lithium battery, lithium ions are released from a positive active material, such as, for example, a lithium-transition metal oxide, and are transferred to a negative active material such as, for example, graphite, where the ions are intercalated into the negative active material.
Due to the high reactivity of lithium, the lithium salt in the electrolyte can react on the surface of the negative active material and a compound such as Li2CO3, Li2O, LiOH, and/or the like may be produced. These compounds may form a SEI (solid electrolyte interface) film on the surface of the negative active material, and the SEI film may act as an ion tunnel, allowing for the passage of lithium ions.
Through this ion tunnel effect, the SEI film prevents (or reduces) damage to the structure of the negative electrode, which can be caused by co-intercalation of high molecular weight organic solvents, along with solvated lithium ions, into the interlayers of the negative active material.
In addition, the SEI film prevents (or reduces) contact between the electrolyte and the negative active material, thereby preventing (or reducing) decomposition of the electrolyte. Accordingly, the lithium on content of the electrolyte is reversibly maintained, and stable charge and discharge characteristics may be realized.
However, the SEI film is not thermally stable and can be damaged or destroyed by increased electrochemical energy and thermal energy resulting from operation of the battery or from allowing the battery to stand at a high temperature. If the SEI film is destroyed and the negative electrode is left without a protection layer, cycle-life characteristics and performance of the battery may deteriorate.